Conventional soft or flexible corneal contact lenses are made of a hydrated gel polymer, commonly poly(hydroxythylmethacrylate) (HEMA). Conventional hard contact lenses are made of poly(methylmethacrylate) (PMMA). Other corneal lenses include gas permeable lenses (typcially copolymers of PMMA with silicone or styrene) and silicone along in resin or elastomer form. Various techniques are known for tinting such contact lenses. One effective technique for tinting soft lenses is set forth is Meshel et al. British Patent No. 1.547.525.
The use of corneal lens with an area of opacity has a wide variety of potential applications. For cosmetic use, a ring conforming to the iris may be formed of semi-opaque material which can be dyed to the desired color. In this way, any color change of the wearer's iris may take place, say from brown to blue or front light to drak, or vice versa. Also, the lens may be used as a prosthesis for the damaged or light sensitive eye. Another advantage of an semi-opaque technique would be to provide a coded symbol, say to left and right lens or of the lens or manufacturer's logo or lot number.
A number of techniques have been suggested to impart opacity to a limited region of a contact lens. One suggestion has been made to add light reflecting particles such as finely divided oyster shell or mica in a matrix of transparent colored lens material. This is suggested for use in a cosmetic soft contact lens. There are several disadvantages to this approach. One is the difficulty in adding the particles to the lens material in a consistent manner and in controlling the hydration and, therefore, power predictability and physical construction of the manufactured lens. Also, the lens material tends to separate from the particles at their interface. Furthermore, such technique must be accomplished before the lens is finished adding to the expense and limiting the technique's versatility. Another problem with this technique is that particles at the lens surface can cause substantial irritation to the eye.
In another suggested technique an semi-opaque material containing plastic insert is interposed between integrally bonded layers of polymer to form a soft contact lens. This technique, suggested in Witcherle U.S. Pat. No. 3,557,261, has not been used commercially. It is subject to a number of disadvantages including the high expense of forming the multiple layer contact lens and separation at the interface of the bonded layers.
Another technique is suggested in Foley, Jr. U.S. Pat. No. 4,252,421 in which a tinted button is polymerized, placed into a mold and a hydrogel co-monomer mixture is mixed around the periphery of the button and polymerized. In another method disclosed in the patent, a clear button is polymerized initially to form a central aperture and a co-monomer mixture including the dye is poured within the aperture and polymerized. This is another complicated technique.
Laser technology has been suggested for a variety of uses with contact lenses, but not to render them semi-opaque. For example, in Brucker, U.S. Pat. No. 3,833,786, laser beams have been suggested for fenestration of contact lenses. Lasers have also been suggested for use in engraving surface indicia on contact lenses in Fischer et al. U.S. Pat. No. 4,194,814. There, the indicia are formed by sublimating lens material with high intensity beam of radiation. The depth of sublimation at the surface of the lens is stated to be controlled to provide relief zones in the form of the desired coating.
There is also a need to mark an intraocular lens, e.g., to encode manufacturing information. Zdrok et al. U.S. Pat. No. 4,039,827 suggests exposing the lens to ultraviolet radiation to produce a differential in refractive index on the surface of the lens.
There is a need for a versatile, inexpensive procedure for forming an semi-opaque region in a contact lens which does not change the essential fitting characteristics of the lens and maintain wearing comfort of the lens.